1. Field of Invention
The invention relates to a method of generating an image of a single document, and more particularly to a method of generating an image of a single document by way of skew correction and image separation.
2. Related Art
When a conventional sheet-fed scanner is performing a sheet-fed scanning operation, a sheet-feeding mechanism transports a plurality of documents across a scan region one by one so that a scanning module of the scanner may scan these documents and acquire the corresponding images. However, when rollers of the sheet-feeding mechanism are worn or the user does not correctly place the documents, a skew or inclination of the document images is particularly likely to occur.
FIG. 1 is a schematic illustration showing a document 100 to be scanned by a conventional sheet-fed scanner. FIG. 2 is a schematic illustration showing a scanned result obtained after the conventional sheet-fed scanner scans the document 100. As shown in FIG. 1, the scanner detects a leading edge 101 of the document 100 by using a document detector. A scanning module of the scanner starts to acquire the image of the document after a period of predetermined time has elapsed or after a stepping motor for driving the sheet-feeding mechanism has rotated by a predetermined number of steps.
However, a detection error might occur when the detector is detecting the leading edge 101 of the document 100, which in result affects the timing of the initiation of the image acquisition. If the scanning module acquires the image too early, the image at a trailing edge 102 of the document may be lost. If the scanning module acquires the image too late, the image around the leading edge 101 of the document may be lost.
In addition to the problem of detection error, the deformation of the image resulting from the skew of the transported document 100 has become a concern of the users. As shown in FIG. 2, four corners 110, 120, 130 and 140 of the document 100 fall outside a scan range 200. Thus, the image data at the four corners 110, 120, 130 and 140 may be lost.